Many devices, including computers and electric vehicles, are powered by secondary (rechargeable) batteries, such as lithium-ion, nickel cadmium, nickel-metal hydride and lead acid batteries. Many of these devices consume enough electricity to require that conventional secondary batteries be connected collectively in modular form, such as in battery modules of six, eight, or up to several dozen batteries per module. Devices may operate at voltages requiring series connections of cells to achieve this voltage. Parallel connections of cells increase the total energy capacity available. However, secondary batteries, such as the lithium-ion secondary batteries, typically can vary from cell-to-cell and, therefore, must be monitored (for safety, life, discharge and charge limits) during charging and discharging. When necessary, they must be charged separately or selectively discharged in order to balance the cells in each battery module and maximize the collective efficiency and utilization of the individual cells.
Further, some cells have shorter cycle lives than others within a single battery module, and it can be difficult to selectively access and replace individual modules, thereby deleteriously affecting the performance of the battery system and the device as a whole. This, in addition to an inability of many battery systems to identify individual cells failing within a module, often requires that the module be replaced, thereby adding to the expense of maintenance associated with the battery system, and reducing the efficiency and utility of the device relying upon the battery system.
Therefore, a need exists for a modular battery system that overcomes or minimizes the above-referenced problems.